Hydraulic blankholder press and operating circuit therefor



July 15, 1952 F. E. SEBRING ETAL HYDRAULIC BLANKHOLDER PRESS AND OPERATING CIRCUIT THEREFOR Filed Feb. 25, 1949 2 SHEETS-SHEET l mvsrrroras FRANK E. SEBRING .mLuAn H. BENNETT ATTORNE Y July 15,- 1952 F. E. SEBRING ET AL 2,603,176

HYDRAULIC BLANKHOLDER PRESS AND OPERATING CIRCUIT THEREFOR Filed Feb. 25, 1949 2 SHEETS--SHEET 2 awe/who'd FRANK E. SEBRING WILLIAM H. BENNETT Patented July 15, 1952 HYDRAULIC BLANKHOLDER PRESS AND OPERATING CIRCUIT THEREFOR Frank E. Sebring and William Hammond Bennett, Mount Gilead, Ohio, assignor to H-P-M Development Corporation, Mount Gilead, Ohio, a corporation of Delaware Application February 25, 1949, Serial No.-78,416

'5 Claims. 1

This invention relates to metal working equipment and especially to drawing presses of the blankholder type.

More particularly still, this invention relates to blankholder presses wherein the blankholder actuating pistons extend into cylinders carried on the main press platen.

In the operation of blankholder pressses where in the blankholder is suspended from the main platen and actuated thereby, the blankholder cylinders are usually connected with thefluid source for the press during the retraction stroke of the main platen in order to return the blankholder to its extended position.

In many instances the size of the blankholder cylinders and plungers is such that the filling of the said cylinders from the fluid source materially detracts from the rate of speed at which the press platen retracts from its working position. Over a period of time during which many working cycles of the press take place, this delay in the retraction of the platen amounts to a considerable length of time and represents a substantial loss in working capacity of the press.

The primary object of the present invention is to provide an actuating circuit for a blankholder press'wherein the blankholder is carried on and actuated by the main platen and wherein the retractionspeed of the main platen is increased by disconnecting the blankholder cylinders from the fluid source.

Another object of this invention is to provide a control circuit for a blankholder type press wherein the blankholder is momentarily energized at the beginning of the retraction stroke of the main platen for stripping the workpiece from the drawing punch.

Still another object is the provision of a blankholder press having a plurality of blankholder pistons and cylinders in which each of the'said cylinders can maintain an independent pressure during the working stroke of the press and in which the blankholder is momentarily energized at the beginning of the retraction stroke of the main platen to strip the workpiece from the forming punch.

These and other objects of this invention will be better understood on reference to the following description taken in connection with the accompanying drawings in which:

Fig. l is a diagrammatic view of a blankholder press constructed according to this invention andshowing the hydraulic operating circuit with control valves;

Fig. 2 shows an electrical control. circuit for controlling the valves in accordance with this General arrangement A press according to this invention comprises a main platen having suspended therefrom a blankholder platen. Piston-cylinder means in- .terconnect the platens so that when the blankholder platen is moved toward the main platen a pressure can be exerted thereon by restricting the discharge of fluid from said piston-cylinder means. This restriction of the discharge is accomplished by suitable relief means adjusted to open at the proper pressure.

In a press of this type it is usually necessary to strip the workpiece from the forming punch after a drawing operation. To accomplishthis it is customary to connect the blankholder cylinders with the retractionarea of the main ram of the press to receive pressure fluid therefrom during the retraction stroke of the main platen. This efiectively *strips the workpiece from the drawing punch but at the same time diverts a large amount of the pumped fluid to the blankholder cylinders and thus causes a reduction in the retraction speed of the main platen.

According to this invention the blankholder cylinders are only momentarily connected with the retraction side of the main ram, just for a sufiicient length of time to dislodge the workpiece from the drawing punch. Thereafter the blankholder cylinders are disconnected from theretraction side of r the ram and are connected instead with. the press reservoir, or with the advancing means of :the ram which at that time is connectedwith the reservoir. This permits the blankholder cylinders to fill by gravity and directs the entire discharge from the fluid source to the retraction side of the main ram.

Since only a slight movement'of the workpiece on the punch is required for breaking the connection theaebetween, this arrangement provides for the continued stripping of the workpiece and permits the blankholder to move to itsfully extended position during the retraction stroke of the ram. I i

According to this invention the connections between the blankholder cylinders and. the I main and retraction sides of the main ram are accomcase the major portion of the retraction stroke oi the main ram takes place with the blankholder cylinders connected with the press reservoir or with the main ram advancing means.

Structural arrangement Referring to the drawings, the press platen is indicated at In and suspended therefrom, as by the rods I2, is a blankholder platen l4 having thereon the blankh'older pistons l6 thatproject .into the blankholder cylinders [B in the platen It.

The platen I is carried on a double acting ram having an advancing pressure area 22 and a relatively smaller retracting area 24. The ram 26 reciprocates in a press cylinder 26 which mounts on its upper end a reservoir 28. A surge valve 36 is mounted in theupper end of the cylinder 26 and affords communication between'the reservoir 28 and the advancing area 22 in response to a predetermined suction .in the upper end of the cylinder; or in response toa predetermined pressure conducted to a pilot operator' 32 of the surge valve by" the conduit 3 which leads to the lower end of the cylinder at.

A reversible variable delivery pump 36 is provided and is connected between the advancing and-the retracting areas of the cylinder. In

the usual manner, spring means, not shown, associated with the control member of the pump,

normally conditions the pump to deliver fluid to the retracting area and a solenoid Si connected with'the control member of the pump operates to shift the pumping means to deliver to the advancingarea of the cylinder. It will be apparent for the purposes of the present invention, that the "pump 36 could be replaced by the combination of a unidirectional pump and a reversing valve.

The control member of the pump is provided with a push rod 4| in opposition to its associated spring means which is engaged by one end of a lever '40 which is abutted by a rod 42 when'the platen 16 reaches its fully retracted position, as

shown in Fig. 1, to shift the control member of the pump to a center or neutral position.

During the rapid advancing movement of the ram 20 make-up fluid is supplied to the upper end of the cylinder 26 from the reservoir 28 through 'a check valve 44 which opens into the conduit 34- connected with the pilot operator and surge valve 30.

The blankh'older'cylinders l8 are interconnected bya channel 46,"and'are also connected by a conduit 48 with the inletof an adjustable pressure relief valve 56 which has its discharge side connected by a conduit 52 with a passage 55 in the ram 20 which is continuously in communication with the retracting area of the cylinder 26.

The ram 20 also comprises a passage 56-which is continuously in communication with the advancing area of the cylinder and which is also connected with a conduit 58 leading to one of the motor ports of a valve 60. The valve 60 also has a motor port connected by a conduit 62 with the conduit 52. The valve 60 includes a third port connected by a conduit 64 with the inlet of a check valve- 66 that opens .into the conduit 48. A valve member 68 in the valve 66 is continuously urged by a spring 10 toward a position to interconnect the conduits 62 and 64 and is adapted for movementin response to the actuation of fluidpressure-responsive pilot plunger 12 into a position to interconnect the conduits 58 and 64.

The pilot plunger 12 is reciprocable in a pilot cylinder 14 carried at one end of the valve 60, and which is connected by a conduit 16 with a pilot valve 78. The pilot valve has an inlet port connected by a conduit 86 with the conduit 52 and also has exhaust ports connected by conduits 82 with the reservoir 28 or any other suitable exhaust receiver.

A valve member 64 inthe valve 181 is 'continuously urged by a spring 86 into a position to connect the conduit 16 with the exhaust conduits 82 and is adapted. for being moved by energizetion of a solenoid S2intc position to connect the conduit 76 with the conduit 80.

In Fig. 1 there will also be seen the limit switches LSi, LS2 and LS3 and the pressure switch PS. The limit switches LS! and LS3 are normally closed and are opened respectively by engagement with a cam 88 carried on the platen 0 at the upper and lower limits of movement of the platen. The limit switch LS2 is also normally closed and is preferably positioned to beengaged by the cam 88 and opened slightly before the said cam engages and opens the limit switch LS3.

The pressure switch PS is connected to receive pressure fiuid from the advancing area of the cylinder 26 and is alsolnormally closed.

The aforementioned solenoids Si and S2, the several limit switchesandthe pressure switch PS are interconnected in an electrical control circuit, one formof which is indicated in Fig. 2.

In Fig. 2 there is a relay switch C which is connected in series between the power lines Li and L2 with a normally open push button switch 90, the limit switch LS3, a normally closed push button switch 92, and the pressure switch PS. The push button switch 90 is bypassed by the normally open switch blade'Cl of the relay C. A second switch blade C2 of the relay C is in series between the lines LI and L2 with the solenoid SI. A third switch blade C3 of the relay C is normally closed and is in series between the'lines LI and L2 with the limit switch LSI, the limit switch LS2, and the operating solenoid S2 of the valve 18.

In operation, an advancing stroke of the ram 26 can be started by closing the push button switch 90. This energizes the relay C, closing the blades Ci thereof to provide a holding circuit for the said relay, closing the blades C2 thereof to energize the solenoid SI and to shift the control member. of the pump to deliver fluid to the advancing area of the cylinder 26 and to withdraw fluid from the retracting area thereof. The blade C3 of the relay C is also opened to open theoperating circuit of the valve solenoid S2. It will be observed that while the platen i 0 is in its fully retracted position the limit switch LSi is open. Thus, while the press platen is retracted, and during its advancing movement, the solenoid S2 is maintained de-energized.

It will be observed that when the solenoid S2 is deenergized the pilot cylinder 14 is exhausted so that the valve member 68 is in its right hand position and connects the retracting area of the cylinder 26 with the inlet of the check valvefili. The press platen moves downwardly until the blankholder engages the work and thereafter continues itsmovement while the said blankholder dwells against the work. Continued movement of the platen displaces fluid from the blankholder cylinders I8 and this fluid is discharged through the relief valve 50 at whatever pressurethe said relief valve is adjusted to discharge.

After the press platen has advanced to the end of its stroke, the cam 88 engages and opens the limit switch LS3 thereby de-energizing the relay C and therethrough also de-energizing the solenoid SI. This initiates the retraction stroke of the press ram and platen by directing the pump discharge to the retracting area of the cylinder 26. It will be observed that the limit switch LS2 at this time is also opened by the cam 88. Since the limit switch LS2 is open the solenoid S2 remains tie-energized and maintains the exhaust corinection to the pilot cylinder 14. This permits the pressure supplied to the retracting area of the ram to be conveyed by way of the valve 68 and check valve 65 to the blankholder cylinders and to act on the blankholder pistons thereon to urge the blankholder downwardly.

However, when the press ram and platen have retracted a predetermined distance, the cam 88 runs over the limit switch LS2 and causes the said switch to close.

Reference to Fig. 2 will reveal that at this time the circuit through the solenoid S2 is completed and the solenoid is therefore energized to move the valve member 84 upwardly and to connect the pilot cylinder 14 through the conduit 88 with the conduit 52 leading to the channel 54 which is in direct communication with the retracting area of the ram.

The supply of pressure fluid from the retracting area through the valve 18 to the pilot cylinder 14 is now effective to shift the valve member 68 lefte wardly and to interrupt communication between the conduits 62 and 64 and, instead, to connect the conduit 64 with the conduit 58 leading to the advancing area of the ram.

During the continued retraction movement of the press ram and platen the blankholder cylinders l8 will thus be filled by fluid from'the ad vancing area of the cylinder. tially gravity filling of the blankholder cylinders, but some slight positive pressure will be available due to the pressure generated by the surging of the fluid on the advancing area of the cylinder through the valve 38.

When the platen completes its retraction stroke, the cam 88 will engage and open the limit switch LSI whereupon the valve solenoid S2 will be de-energized to return the valve member 84 into position to exhaust the pilot cylinder 14. This again permits the valve member 68 to return to its right hand position but at this time there will be not less of fluid from the retracting area of the cylinder to the blankholder cylinders l8 because the pistons It will be fully extended in the said cylinders.

It will be apparent that the circuit described above provides for temporary independent energization of the blankholder rams from the retracting area of the press during the initial portion of the retraction stroke, in order to break the blankholder free and to commence the stripping of the workpiece from the press punch. However, after the blankholder has been broken free and further movement thereof can be ac complished relatively easily, further filling of the This is substan holder from the retracting area of the press ram,-

blankholder cylinders 'isby gravity so that the entire discharge'of the pump can be directed to theretractingfarea 'o'f the press ram. This provides for a rapid retraction stroke of the 'press blankholder cylinders, each of the said-cylinders, as indicated at [8a, l8b in Fig. 3, may be provided with individual relief-valves as indicated at 58a and 582). In this case, the blankholder cylinders are connected with their associated relief valves by. individual conduit means as indicatedat 48a and 48b, and between each of the said'conduits and the control valve 68 is an individual check valve as illustrated at 68a, 66!).

In the modification shown in Fig. 3 it will be apparent that the operation of the blankholder is the same as described in connection with Fig. 1 except that individual pressures can be maintained in the blankholder cylinders during the working stroke of the press.

Since an essential feature of this invention constitutes the temporary energization of the blankholder from the retraction area of the press ram at the beginning of the retraction stroke of the press platen, other means may be provided for controlling the connection of the blankholder with the retracting area of the ram. Fig. 4 illustrates a modified form of apparatus for accomplishing temporary energization of the blankthe reversal of the press ram and platen, there will be a predetermined time delay before the valve solenoid S2 becomes energized. This period of delay will correspond with the initial retraction movement of the ram and platen and can be adjusted for any desired interval.

One advantageto be obtained from the modification illustrated in Fig. 4 is that the reversing of the press ram and platen can be accomplished by any means other than a limit switch, such as LS2, which is responsive to the position of the press platen, and without affecting the operation of the control circuit to energize the blankholder temporarily. While in most instances a positionreversal of the press platen will be the most desirable, there may be certain other circumstances, when it is desired to provide for pressure r'eversal of the said platen and at the same time to obtain the temporary energization of the I blankholder to strip the workpiece from the pressing punch.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

We claim;

1. In a drawing press, a main platen having fluid operable advancing and retracting means, a blankholder platen suspended from said main platen and having piston means, cylinder means in said main platen receiving said piston means, relief valve means having an inlet connected with said cylinder means and an outlet connected with said retracting means, a second valve means connected between said retracting means and the inletaoi saidmelief valve means and also-conneoted with said advancing means means-normally conditioning said second valve means --to connect said=retracting means with the inlet of 'saidrelief valve means, and means: operable during the retraction vof said :main platen-Ion conditioning saidsecond-valvezmeans to connect the inlet-of said relief valve means'with' said advancing' means. 7

"2. In a drawing press having a main,platen and a blank-holder platen suspended therefrom,

and movable theretowards, fluid operable advancing and retracting means for said main platen, pistons carried by said blankholderplaten and cylinders in-said mainplaten receivingsaid pistons, a relief valve having an inlet connected with said' cylinders and: an outlet connected with said retractingmeans, conduit means extending from said advancing means to said cylinder means and including a check valveopening-toward the latter, said conduit means also'includ- 'ing valve means normally positioned to interrupt the said conduit andalso havinga'connection with said retracting means, means operable during retracting movement of said main platen 'for conditioning said last-named valve means advancing and retracting means, said valve being normally positioned to connect said retracting means with said cylinder means and being movable to connect said cylinder means with said advancing means; means for actuating said valve by pressure fluid in said retracting means. and means responsive to retracting movement of said main platen for directing pressure fluid from said retracting means to said valve to move the latter to connect said cylinder means with said advancing means.

' i. In a blankholder press; a main platen; a hydraulic motor connected to reciprocate said main platen and having fiuidr-pressure-responsive advancing andretracting areas; a blankholder platen suspendedfrom saidmain platen and, movable relative thereto; piston-cylinder means connected between said main platen and said blankholder platen for yieldably resisting movement of said blankholder platen toward said ,main platen; a relief valve connected with said piston-cylinder means for discharging fluid having connections respectively with said piston- 7 second valve including a Valvemember normally positioned to connect said piston-cylinder means with the retracting area of said motor, but being movable to connect said piston-cylinder means with the advancing area of said motor; -a check valve interposed between said piston-cylinder means and said second valve for permitting the passage of fluid only ina direction from said second valve toward saidpiston-cylinder means; and other means connected with the valve member ofsaid second valve and operable during the retraction of said main platen for moving the valve member to a position to connect said pistoncylinder means with the advancing area of said motor.

5.- In a drawing press; a mainwplaten; a hydraulic motor connected to reciprocate said main platen and having advancing and retracting areas; a blankholder platencarriedby said main platen and movable theretoward; piston-cylinder'means connected between said blankholder platen and'saicl main platen for yieldably resisting movement of said blankholder platen toward said main platen; a relief valve connected to exhaust fluid from said piston-cylinder means at a given high pressure; a distributing valve having connection respectively with the advancing area of said motor, the retracting area of said motor, and said piston-cylinder means, and having a valve member movable to connect said piston-cylinder'means with either the advancing or retracting areas of said motor; a check valve connected between said distributing valve and said piston-cylinder means for permitting flow of fluid only in a direction from said distributing valve toward said piston-cylinder means; fluidpressure-responsive means connected with-the valve member of said distributing valve and operable to move the latter to a position connecting said piston-cylinder means with the advancing area'of said motor; and means operable during retracting movement of said main platen for supplying pressure fluid to said fluid-pressureresponsive means and thereby to move the valve member of said distributing valve to its position connecting said piston-cylinder means with the advancing area of said motor.

FRANK E. SEBRING. WILLIAM HAMMOND BENNETT.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,252,881 Ernst Aug. 19, 1941 2,357,019 Nowak Aug. 29, 1944 2,396,296 Stacy Mar. 12, 1946 

